1. Field of the Invention
This invention relates to a method of and apparatus for trimming metal containers and more particularly to a method of and apparatus for trimming excess metal from a flange at the open top end of a drawn cup shaped article.
2. Description of the Prior Art
Metal containers formed by a deep draw process have uneven edges which must be trimmed following the drawing operation. Trimming such edges has presented problems, particularly in the high-speed production of one-piece container bodies such as metal cups and cans used in the packaging of foods, beverages and the like. The excess metal at the uneven top edges of such containers is conventionally removed in an annular ring by a die cutting operation at the end of the final drawing step, or by a spin cutting operation following the final drawing step. Removal of the waste trim ring has presented problems particularly since the cutting operation normally leaves the ring telescoped over a part of the apparatus. Removal of the trim ring can also interfere with removal of the trimmed container body from the apparatus and with positioning the next container, or container blank, in the apparatus.
Following the trimming operation in the forming of single piece can bodies, the open top of the trimmed container is normally flanged, i.e., a narrow, outwardly directed flange is formed at the open top to facilitate closing the filled container with a metal closure panel by a roll seaming operation. It has also been known to form the closure attachment flange by terminating the final drawing step prior to drawing all of the metal into the die, thereby leaving a relatively wide flange, which includes the scrap which is to be removed, then trimming the flange in a die cutting operation. Such a trimming operation is disclosed in U.S. Pat. No. 3,855,862 wherein the sidewalls are initially ironed at a diameter greater than desired for the finished container, and then redrawn to reduce the diameter and form the flange which is trimmed at the end of the final draw. The scrap ring is removed in one piece by a die cutting operation, leaving the desired flange in the previously ironed sidewall metal at the open top. Again, the one-piece trim ring presented problems of removal and disposal.
Attempts have been made to remove the trim metal from the top of a deep drawn container in sections to facilitate removing and handling of the severed scrap. One such prior art device is disclosed in U.S. Pat. No. 2,074,547 wherein the excess, uneven material is removed from the open top of the container by a pair of shearing dies moved substantially perpendicular to the axis of the container by a camming operation. Thereafter a second pair of cutters are moved substantially perpendicular to the direction of movement of the cam actuated shears to slit the severed ring into two segments to facilitate scrap removal. This apparatus was necessarily relatively slow and unsuited for present day high-speed can forming apparatus.
Another prior art device for trimming drawn containers is disclosed in U.S. Pat. No. 4,257,293 and includes a plurality of cam actuated cutters disposed radially around a mandrel supporting a can to be trimmed. The cams are actuated in sequence to move the cutters into engagement with and trim the waste material which is permitted to fall into a removal chute.
U.S. Pat. No. 3,913,372 discloses apparatus for forming a container closure from a flat metal blank by a punch and die operation and for removing an annular wastage ring from the formed closure. The severed ring is cut into segments for removal by pressing the ring against spaced cutters located around the forming die.
U.S. Pat. No. 3,881,380 discloses mechanism for trimming the open end of a one-piece metallic can body supported on a mandrel by initially cutting a scrap ring from the open end of the supported can and thereafter actuating two scissors-like nipper devices located on opposite sides of the mandrel to severe the scrap ring into two pieces which are permitted to fall into a scrap disposal chute.